Html5,jquery,ajax Basic Interview

Brief description of local storage in HTML5

Answer:

Most of the time we store the user's local information on the computer, for example: The user has a long table filled in half, then suddenly the network connection is broken, so the user wants you to store this information locally, when the network replies, he wants to get this information and then send to the server for storage,

Modern browser-owned storage is called "Local storage" for storing this information

Briefly describe the role of canvas in HTML5

Answer: The new tag that appears, has its own properties, methods, and events, where there is a way to draw, JavaScript can invoke it to complete the drawing on a Web page

Canvas is also one of the most powerful features in HTML5, allowing developers to implement desktop application functionality on the Web using dynamic and interactive visualization methods

What are the different types of storage for HTML5?

Answer:

HTML5 supports local storage and is implemented via cookies in previous versions, HTML5 local storage is fast and secure

There are two different kinds of objects that you can use to store data:

Localstorage: For long-term storage of data, no loss of data after browser shutdown

Sessionstorage: Stored data is automatically deleted when the browser is closed

HTML5 What other media elements are supported in addition to audio and video?

Answer: <EMBED>: As a container for external applications;

<track>: Defining text tracking for media

<SOURCE>: Support for multiple media sources

What is the HTML5 app cache?

Answer: Often used to show users offline browsing if the network connection is not available, the page should be from the browser cache, the offline application cache can help you achieve this goal

Application caching can help you develop those files that need to be cached and which are not.

Jquery

The onload () function in the body and $ (document) in JQuery. Reay () What's the difference?

Answer:

The difference between onload () and Document.ready () is as follows:

Multiple Document.ready () can be used in the page, but only one time onload () is used;

The Document.ready () function is called when the page DOM element is loaded, and the onload () function is called when all associated resources (including images, audio) are loaded.

What kinds of selectors are there in jquery?

Answer:

There are three types of selectors:

1 Basic selector: Returns DOM elements directly based on the ID CSS class name element name

2 Hierarchy selector: Also called the path selector, you can select the appropriate DOM element according to the path hierarchy

3 Filter Selector: Filter the relevant conditions on the previous basis to get a matching DOM element

Please describe the Xmlhttpquest object

Answer:

The core of Ajax is the JavaScript object XMLHttpRequest. This object was first introduced in IE5, a technique that supports a request, in short, XMLHttpRequest can use JavaScript to request and process the response without blocking the user, through XML HttpRequest objects, Web developers can make page local updates at a later time in the page home

The pros and cons of Ajax

Advantages: page local refresh, improve user experience

Communicate with the server in one way, with more rapid response capability;

reduce server burden;

The technology that gives standardized disease-managed rice support does not require downloading plugins or small programs.

Disadvantages:

The Back button of the browser is not supported

Security issues

Support for search engines is relatively weak

Html5,jquery,ajax Basic Interview